Heat Recovery Ventilation Efficiency Ratings

hebridean

I'm in the market for a whole house system and have received quotes from a few companies. The companies systems are on the SAP efficiency database and i've found that the 90% efficient systems are around £3500 though one quote was £5500. The 70% efficient system quote i received was £2400, and as i've read that the average running costs per anum for the 90% system is about £40 i'm thinking that the 70% systems running costs would be about £55 per anum.
Does anyone know how this efficiency rating is measured ie the exchangers performance or power consumption etc?.
My thinking being that if the annual runing costs for the less efficient system amounts to an extra £15 per anum and the life expepectancy for all systems is say ten years then the cheaper unit would be considerably cheaper in the long run.
Does anyone have any experience/opinions on these systems?

bobmedley

Hi there

We have a Villavent system that has now been running for 10 years with no problems - it's a 70% efficient model as nothing higher was available at the time.

As for running costs, you are being told the price in electricity of running the unit i.e. what the fans use. This depends entirely on how you use it, because they have different settings that obviously vary the amount of power they draw. We tend to leave ours on one setting and that is 60w, so over a year that totals c£50.

Regarding the 70% v 90% units for comparison of how they affect your fuel bills, that is the $64,000 question. It would be a quite complicated calculation as it would depend entirely on how you use the system, your house's insulation and other factors. One thing is certain though, you can't just look at your overall fuel bills and say that the 90% unit will save c28.5% (90%/70%) of your fuel costs over the 70% unit as they simply do not draw out all of the heat in your house.

Overall we are very happy with the system. primarily as it's cut condensation to virtually zero.

HTH

PS For the reasons above, I would go for the cheaper system

PPS It's also important to go for a model with a summer block (straight pass through of air) - this replaces the heat exchanger in Summer so you don't bring in warmer air when your house does not need it

hebridean

Thanks for the reply Bob, and from your own experience it would seem to make more sense to buy the cheaper unit as you suggested.
I'm waiting for another couple of quotes and expect them to be in the £3500+ bracket.

arty68

There's also the sap Q thing to think about, if you feel a higher score for your house is important to you or maybe important in the future when you come to sell.
Also the actual difference in price of the HR unit its self is not £1100 so I would guess the cheaper quote is for a lesser system regarding ducting and controls etc. and how much air it can shift. Make sure you are comparing like with like.
So I would ask the compaines :-
1. What ducting
2. What controls
3. Summer bypass
4. Controls
5. How much air the unit can shift
6. Noise levels


If everything is the same I would ask the people who quoted you £2400 how much they would charge for an upgraded unit.

One last point the price they give you to start with will change if you haggle and play one off against another they are all desparate for you business.

hebridean

Thanks for your reply Arty68, and i've researched the £2400 units capabilities and found that it is very similar in most aspects as the more expensive units. I hadn't however thought of doing a bit of haggling and intend doing so once i get another couple of quotes i'm waiting for. In fact i also think i'll do the same with a couple of ASHP quotes i've got!

Cheers